Use more optimal Ord implementation for integers

src/libcore/cmp.rs

@@ -1012,9 +1012,11 @@ mod impls {
             impl Ord for $t {
                 #[inline]
                 fn cmp(&self, other: &$t) -> Ordering {
-                    if *self == *other { Equal }
-                    else if *self < *other { Less }
-                    else { Greater }
+                    // The order here is important to generate more optimal assembly.
+                    // See <https://github.com/rust-lang/rust/issues/63758> for more info.
+                    if *self < *other { Less }
+                    else if *self > *other { Greater }
+                    else { Equal }
                 }
             }
         )*)

src/test/codegen/integer-cmp.rs

@@ -0,0 +1,28 @@
+// This is test for more optimal Ord implementation for integers.
+// See <https://github.com/rust-lang/rust/issues/63758> for more info.
+
+// compile-flags: -C opt-level=3
+
+#![crate_type = "lib"]
+
+use std::cmp::Ordering;
+
+// CHECK-LABEL: @cmp_signed
+#[no_mangle]
+pub fn cmp_signed(a: i64, b: i64) -> Ordering {
+// CHECK: icmp slt
+// CHECK: icmp sgt
+// CHECK: zext i1
+// CHECK: select i1
+    a.cmp(&b)
+}
+
+// CHECK-LABEL: @cmp_unsigned
+#[no_mangle]
+pub fn cmp_unsigned(a: u32, b: u32) -> Ordering {
+// CHECK: icmp ult
+// CHECK: icmp ugt
+// CHECK: zext i1
+// CHECK: select i1
+    a.cmp(&b)
+}